Intraocular lens, method for designing the same, and method for manufacturing the same

ABSTRACT

Provided is an intraocular lens including a lens body having a back surface disposed on a retinal side and a front surface disposed on a corneal side, wherein an entire back surface is shaped in such a way as to protrude from a peripheral edge of the back surface toward the retinal side in a direction of an optical axis, in a shape of a truncated cone, and the front surface has any of the following shapes (i) to (iii);
         (i) the front surface is shaped in such a way as to start to be recessed toward the retinal side in the direction of the optical axis when viewed toward a center from a peripheral edge of the front surface,   (ii) the front surface is shaped in such a way that an initial part from the peripheral edge of the front surface toward the center is flat,   (iii) the front surface is shaped in such a way as to start to protrude toward the corneal side in the direction of the optical axis when viewed toward the center from the peripheral edge of the front surface, but a rate of rise of a protrusion from the peripheral edge of the front surface is smaller than a rate of rise of a protrusion from the peripheral edge of the back surface.

TECHNICAL FIELD

The present invention relates to an intraocular lens, a method ofdesigning the same, and a method of manufacturing the same.

BACKGROUND ART

An intraocular lens which plays a role in the correction of a visualfunction after removing a crystal lens opacified by a cataract is known.For example, when a crystal lens is opacified due to a cataract, arecovery of vision is attempted by a surgical procedure which inserts anartificial intraocular lens in a crystalline lens capsule, in place ofthis opaque crystal lens.

It is required to suppress a secondary cataract after inserting anintraocular lens into the crystalline lens capsule (Patent Document 1).The secondary cataract is a phenomenon in which lens epithelial cellsmigrate to the posterior of the intraocular lens, i.e., into the gapbetween the lens body of the intraocular lens and the posterior capsule,which causes fibrosis or swelling and degeneration, and opacifies theposterior capsule of the crystal lens capsule.

Further, it is also required to make a small incision when inserting theintraocular lens into the crystal lens capsule. In order to make thesmall incision, it is effective to insert the intraocular lens into thecrystal lens capsule in a folded state (Patent Document 2).

Furthermore, after the intraocular lens is inserted into the crystallens capsule, it is also required to stably place the intraocular lensinto the crystal lens capsule (i.e., intracapsular stability) (PatentDocument 3). The intracapsular stability is required, specifically, in atoric intraocular lens.

CITATION LIST Patent Document

[Patent Document 1] WO2003/055416

[Patent Document 2] WO2009/153873

[Patent Document 3] Japanese Translation of PCT InternationalApplication Publication No. 2015-503977

SUMMARY OF INVENTION Technical Problem

The present invention makes as its technical subject to provide anintraocular lens for improving the intracapsular stability whilefacilitating fold of the intraocular lens, and suppressing theoccurrence of a secondary cataract, and a related technology thereof.

Solution to Problem

The present inventor examined an approach completely different from thetechniques described in Patent Documents 1 to 3. As a result, theconfiguration of the present invention described hereinafter isachieved.

The first aspect of the present invention is an intraocular lensincluding a lens body having a back surface disposed on a retinal sideand a front surface disposed on a corneal side, wherein

an entire back surface is shaped in such a way as to protrude from aperipheral edge of the back surface toward the retinal side in adirection of an optical axis, in a shape of a truncated cone, and, thefront surface has any of the following shapes (i) to (iii),

(i) the front surface is shaped in such a way as to start to be recessedtoward the retinal side in the direction of the optical axis when viewedtoward the center from a peripheral edge of the front surface,

(ii) the front surface is shaped in such a way that an initial part fromthe peripheral edge of the front surface toward the center is flat,

(iii) the front surface is shaped in such a way as to start to protrudetoward the corneal side in the direction of the optical axis when viewedtoward the center from the peripheral edge of the front surface, but arate of rise of a protrusion from the peripheral edge of the frontsurface is smaller than a rate of rise of a protrusion from theperipheral edge of the back surface.

The second aspect of the present invention is the invention according tothe first aspect satisfying at least one of the following conditions,

(Condition 1)

in the back surface, a sag value of the back surface at a distance Lp ina region within a predetermined distance from an optical center Cp, to avirtual spherical surface Sp having a curvature radius Rcp at theoptical center Cp, (with this optical center Cp as a vertex), is notmore than a sag value of the virtual spherical surface Sp at thedistance Lp, and a sag value of the back surface at a distance lpoutside of the region within the predetermined distance becomes largerthan a sag value of the virtual spherical surface Sp at the distance lp,and

in the front surface, a sag value of the front surface at a distance Lain a region within a predetermined distance from an optical center Ca,to a virtual spherical surface Sa having a curvature radius Rca at theoptical center Ca, with this optical center Ca as a vertex, is not lessthan a sag value of the virtual spherical surface Sa at the distance La,and a sag value of the front surface at a distance la outside of theregion within the predetermined distance becomes smaller than a sagvalue of the virtual spherical surface Sa at the distance la,

(Condition 2)

in the back surface, a sag average value of the back surface in a regionwithin a predetermined distance from an optical center Cp is not morethan a sag average value of the virtual spherical surface Sp in theregion within the predetermined distance, and a sag average value of theback surface outside of the region within the predetermined distancebecomes larger than a sag average value of the virtual spherical surfaceSp outside of the region within the predetermined distance, and

in the front surface, a sag average value of the front surface in aregion within a predetermined distance from an optical center Ca is notless than a sag average value of the virtual spherical surface Sa insideof the region within the predetermined distance, and a sag average valueof the front surface outside of the region within the predetermineddistance becomes smaller than a sag average value of the virtualspherical surface Sa outside of the region within the predetermineddistance,

(Condition 3)

in the back surface and the front surface, when the sag values thereofare measured at a predetermined number of measurement points equallyspaced from each other, there are half or more measurement points whichsatisfy Condition 1, inside and outside of the region within thepredetermined distance,

wherein the sag value is a vertical distance from a tangent plane at theoptical center, to the virtual spherical surface,

distances Lp, lp, La and la are the distances from the optical centerwhen viewed in parallel to the tangent plane,

the sag average value of the back surface or the virtual sphericalsurface Sp is the average value of the sag value at each point inside oroutside of the region within the predetermined distance from the opticalcenter Cp, and

the sag average value of the front surface or the virtual sphericalsurface Sa is the average value of the sag value at each point inside oroutside of the region within the predetermined distance from the opticalcenter Ca.

The third aspect of the present invention is the invention according tothe second aspect,

wherein a peripheral position Ep of the back surface is separated by 0.1mm or more from a peripheral position Eps of the virtual sphericalsurface Sp in a direction vertical to a tangent plane at the opticalcenter Cp, namely, in a direction from the back surface to the frontsurface, the peripheral position Eps being located at a distance of aperipheral edge Ep of the back surface from the optical center Cp on thetangent plane, and

a peripheral position Ea of the front surface is separated by 0.1 mm ormore from a peripheral position Eas of the virtual spherical surface Sain a direction vertical to a tangent plane at an optical center Ca,namely, in a direction from the back surface to the front surface, theperipheral position Eas being located at a distance of a peripheral edgeEa of the front surface from the optical center Ca on the tangent plane.

The fourth aspect of the present invention is the invention according tothe second or third aspect, wherein

an optical function in accordance with a prescription is exhibited in anentire lens body.

The fifth aspect of the present invention is the invention according tothe second or third aspect, wherein

the back surface and the front surface of the lens body respectivelyinclude an effective optical portion which exhibits an optical functionin accordance with a prescription and a peripheral portion disposedaround the effective optical portion.

The sixth aspect of the present invention is the invention according toany one of the first to the fifth aspects, wherein the front surface,the back surface, or both surfaces of the lens body is spherical,aspheric, or a combination thereof.

The seventh aspect of the present invention is the invention accordingto any one of the first to the sixth aspects, wherein the front surface,the back surface, or both surfaces of the lens body have a shape whichis at least one of monofocal, bifocal or multifocal, or tonic, thebifocal and the multifocal being refractive, diffractive, or acombination thereof.

The eighth aspect of the present invention is the invention according toany one of the first to the seventh aspects, further including:

a support portion extending from the lens body.

The ninth aspect of the present invention is a method of designing anintraocular lens including a lens body,

wherein the lens body has a front surface disposed on a corneal side anda back surface disposed on a retinal side, the method including:

step 1 of changing a design of a center portion of the back surface anda center portion of the front surface of the lens body so as to be movedby a predetermined distance to the retinal side in a direction of anoptical axis, the lens body being designed according to a prescription,and

continuously to step 1, step 2 of changing a design of a peripheralportion disposed around the center portion of the back surface so as tosatisfy the prescription and so that an entire back surface is shaped insuch a way as to protrude from a peripheral edge of the back surface, ina shape of a truncated cone, and

changing a design of a peripheral portion disposed around the centerportion of the front surface so as to satisfy the prescription andsatisfy one of the following (i) to (iii),

(i) a peripheral portion of the front surface is shaped in such a way asto start to be recessed toward the retinal side in the direction of theoptical axis when viewed toward the center from the peripheral edge ofthe front surface,

(ii) the peripheral portion of the front surface is shaped in such a waythat an initial part from the peripheral edge of the front surfacetoward the center is flat,

(iii) the peripheral portion of the front surface is shaped in such away as to start to protrude from the peripheral edge of the frontsurface toward the corneal side in the direction of the optical axiswhen viewed toward the center from the peripheral edge of the frontsurface, but, a rate of rise of the protrusion from the peripheral edgeof the front surface is smaller than a rate of rise of the protrusionfrom the peripheral edge of the back surface.

The tenth aspect of the present invention is the invention according tothe ninth aspect which is the method of designing an intraocular lensincluding a lens body, wherein the lens body has the front surfacedisposed on the corneal side and the back surface disposed on theretinal side, the method including:

step 2 of changing a design of the peripheral portion disposed aroundthe center portion of the back surface and the peripheral portiondisposed around the center portion of the front surface in order tosatisfy at least one of the following conditions,

(Condition 1)

in the back surface, a sag value of the back surface at a distance Lp ina region within a predetermined distance from an optical center Cp, to avirtual spherical surface Sp having a curvature radius Rcp at theoptical center Cp, with this optical center Cp as a vertex is not morethan a sag value of the virtual spherical surface Sp at a distance Lp,and a sag value of the back surface at a distance lp outside of a regionwithin the predetermined distance, becomes larger than a sag value ofthe virtual spherical surface Sp at the distance lp, and

in the front surface, a sag value of the front surface at a distance Lain a region within a predetermined distance from an optical center Ca,to a virtual spherical surface Sa having a curvature radius Rca at theoptical center Ca, with this optical center Ca as a vertex is not lessthan a sag value of the virtual spherical surface Sa at the distance La,and a sag value of the front surface at a distance la outside of theregion within the predetermined distance becomes smaller than a sagvalue of the virtual spherical surface Sa at the distance la,

(Condition 2)

in the back surface, a sag average value of the back surface in theregion within a predetermined distance from the optical center Cp is notmore than a sag average value of the virtual spherical surface Sp in theregion within the predetermined distance, and a sag average value of theback surface outside of the region within the predetermined distancebecomes larger than a sag average value of the virtual spherical surfaceSp outside of the region within the predetermined distance, and

in the front surface, a sag average value of the front surface in theregion within the predetermined distance from the optical center Ca isnot less than a sag average value of the virtual spherical surface Sainside of the region within the predetermined distance, and a sagaverage value of the front surface outside of the region within thepredetermined distance becomes smaller than a sag average value of thevirtual spherical surface Sa outside of the region within thepredetermined distance,

(Condition 3)

in the back surface and the front surface, when the sag values thereofare measured at a predetermined number of measurement points equallyspaced from each other, there are half or more measurement points whichsatisfy Condition 1 inside and outside the region within thepredetermined distance.

Note that, the sag value is a vertical distance from the tangent planeat the optical center, to the virtual spherical surface,

the distances Lp, lp, La and la are the distances from the opticalcenter when viewed in parallel to the tangent plane,

the sag average value of the back surface or the virtual sphericalsurface Sp is the average value of the sag value at each point inside oroutside of the region within the predetermined distance from the opticalcenter Cp, and

the sag average value of the front surface or the virtual sphericalsurface Sa is the average value of the sag value at each point inside oroutside of the region within the predetermined distance from the opticalcenter Ca.

The eleventh aspect of the present invention is a method ofmanufacturing of an intraocular lens, including:

a step of manufacturing the lens body designed by the method ofdesigning according to the ninth or the tenth aspect.

Further, other aspects of the present invention are exemplified asfollows.

-   -   An intraocular lens including a lens body having two opposing        surfaces A and B, wherein

an entire surface A is shaped in such a way as to protrude from theperipheral edge of the surface A in a shape of a truncated cone and anentire surface B has a shape which is recessed from the peripheral edgeof the surface B, toward one of the directions of the optical axis.

-   -   An intraocular lens including at least one part of the front        surface having a shape which is recessed (preferably, the entire        the front surface is recessed in a shape of a truncated cone)        more than the peripheral edge of the front surface.    -   An intraocular lens including a lens body having the front        surface disposed on the corneal side and the back surface        disposed on the retinal side, wherein the lens body, viewed from        the peripheral edge of the lens body, has a shape which is bent        toward the retinal side in the direction of the optical axis.

Note that, with regards to surface B or the front surface, thedefinition relating to the front surface in the above describedCondition 1 may be adopted.

Further, the second aspect of the present invention may be an aspect ofan independent invention which is not dependent upon the inventionaccording to the first aspect. Similarly, the tenth aspect of thepresent invention may be an aspect of an independent invention which isnot dependent upon the invention according to the ninth embodiment.

Advantageous Effects of Invention

According to the present invention, the intraocular lens is provided,which improves intracapsular stability and suppresses the occurrence ofthe secondary cataract while facilitating fold of the intraocular lens.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view illustrating a conventional intraocular lens,wherein (a) is a plan view, and (b) is a side view viewed from an arrowx.

FIG. 2 is a schematic plan view and a schematic cross-sectional sideviews (a) to (f) illustrating a method of designing and a method ofmanufacturing the intraocular lens according to the present embodiment.

FIG. 3 is a schematic cross-sectional side view illustrating the lensbody of the present embodiment, wherein (a) illustrates a lens body inwhich the back surface is a convex surface and a front surface is a flatsurface according to a conventional art, and meanwhile (b) illustrates astate after a change in design (corresponding to (i)) is performed tothe back surface and the front surface according to the presentembodiment.

FIG. 4 is a schematic view illustrating the intraocular lens of thepresent embodiment, wherein (a) is a plan view, and (b) is across-sectional side view of a cross section taken along a straightbroken line viewed from arrow X.

FIG. 5 is an expanded view of a portion surrounded by the broken line ofFIG. 4.

FIG. 6 is a schematic cross-sectional side view illustrating anotheraspect of the lens body, wherein (a) illustrates the lens body in whichthe back surface and the front surface are convex surfaces according toa conventional art, and (b) illustrates the state after a change indesign (corresponding to (i)) is performed to the back surface and thefront surface according to the present embodiment.

FIG. 7 is a schematic cross-sectional side view illustrating anotherembodiment of the lens body, wherein (a) illustrates a lens body inwhich the back surface is a flat surface and the front surface is aconvex surface according to a conventional art, and (b) illustrates astate after a change in design (corresponding to (i)) is performed tothe back surface and the front surface according to the presentembodiment.

FIG. 8 is a schematic cross-sectional side view illustrating anotherembodiment of the lens body, wherein (a) illustrates a lens body inwhich the back surface is a flat surface and the front surface is aconvex surface according to a conventional art, and (b) illustrates astate after a change in design (corresponding to (iii)) is performed tothe back surface and the front surface according to the presentembodiment.

FIG. 9 is an expanded view in the vicinity of the peripheral edge of thelens body after a change in design (iii) is performed to the lens bodyof the conventional art of FIG. 6(a) in which the back surface and thefront surface are convex surfaces.

DETAILED DESCRIPTION OF EMBODIMENTS

The embodiments of the present invention will be described in detailhereafter, with reference to the drawings.

In the present embodiment, the explanation is performed in the followingorder.

1. Method of designing and method of manufacturing the intraocular lens

2. Intraocular lens

2-1. Lens body

-   -   2-1-1. Back surface    -   2-1-2. Front surface

2-2. Support portion

2-3. Modified examples or preferred examples relating to the intraocularlens

3. Effect of the embodiment

4. Other modified examples

Note that, regarding configurations not described below, a knownconfiguration may be appropriately adopted. Specifically, the contents(particularly the support portion) described in the reference(WO2009/153873) disclosed by the present applicant may be applied to thepresent embodiment.

Further, the term “to” in the description indicates a value greater thanor equal to a predetermined value and less than or equal to apredetermined value.

Further, the lens body of the intraocular lens taken up in thedescription has two surfaces opposing each other. When the intraocularlens is inserted into the crystal lens capsule, the surface of the lensbody on the side contacting with the posterior capsule may be referredto as the back surface, the surface on the retinal side, or the surfaceon the retinal side in the direction of the optical axis, but the “backsurface” is mainly used in the description. Moreover, it is possible torefer to the other surface as the front surface, the surface on thecorneal side, or the surface on the corneal side in the direction of theoptical axis, but the “front surface” is mainly used in the description.Further, the optical axis direction is also a lens thickness direction,and is a direction from the back surface toward the front surface orvice versa.

1. Method of Designing and Method of Manufacturing the Intraocular Lens

First, the intraocular lens in the present embodiment includes a lensbody having a lens function and support portions for supporting the lensbody in the crystal lens capsule in the same manner as a conventionalintraocular lens. FIG. 1 is a schematic view illustrating a conventionalintraocular lens, wherein (a) is a plan view and (b) is a side viewviewed from an arrow X. Note that, reference numeral 100 indicates aconventional intraocular lens, reference numeral 200 indicates aconventional lens body, and reference numeral 300 indicates aconventional support portion, but hereinafter, these reference numeralswill be omitted.

The method of designing and the method of manufacturing the intraocularlens in the present embodiment are mainly constituted by the followingsteps. Each step (specifically, regarding two design changing stepsdescribed later) is described using FIG. 2. Note that, reference numeral1 indicates the intraocular lens of the present embodiment, referencenumeral 2 indicates the lens body of the present embodiment, andreference numeral 3 indicates the support portion of the presentembodiment, but hereinafter, these reference numerals will be omitted.

(Design)

First, the lens body is designed in accordance with a prescription. Aknown technique may be used as the specific design technique. Note that,a design at this stage is that the back surface as described above doesnot protrude in a shape of a truncated cone (FIG. 2(a)).

(Change in Design 1)

This step (Step 1) and the subsequent step (Step 2) are one of the majorfeatures of the present embodiment. In the step, the center portion ofthe back surface and the center portion of the front surface of the lensbody designed according to the prescription are changed in design so asto move (shift) by a predetermined distance to the retinal side in thedirection of the optical axis (FIG. 2(b)).

A movement distance at this time can be arbitrarily set by a designer.For example, if it is desired to further push the center portion of theback surface to the posterior capsule of the crystal lens capsule, themovement distance may be comparatively large (for example, 0.2 to 0.7mm).

(Change in Design 2)

Following Step 1, in this Step, the back surface is changed in design asfollows (FIG. 2(c)).

The peripheral portion disposed around the center portion of the backsurface is changed in design so as to satisfy the prescription and sothat the entire back surface is shaped in such a way as to protrude fromthe peripheral edge of the back surface in a shape of a truncated cone.

In the present embodiment, the center portion of the back surface andthe center portion of the front surface of a conventional lens bodydesigned in accordance with the prescription (FIG. 2(a)) move (shift) bya predetermined distance to the retinal side in the direction of theoptical axis (FIG. 2(b)), and, there is a reason that the back surfaceof the lens body is formed into the aforementioned shape (FIG. 2(c)).This reason is described below.

The present embodiment adopts a configuration in which the centerportion protrudes from the peripheral edge of the back surface of thelens body, by a portion (the peripheral portion) outside of the regionwithin a predetermined distance from an optical center of the backsurface. At this time, the peripheral portion surrounding the centerportion of the back surface is configured to connect the peripheral edgeof the back surface and the center portion. In short, in the presentembodiment, the back surface of the lens body is changed in design so asto protrude in a shape of a truncated cone, the truncated conecorresponds to the peripheral portion, and a plateau surface of thetruncated cone corresponds to the center portion.

Note that, in the present embodiment, the center portion indicates acenter region within a region of a predetermined distance and includingthe optical center, the peripheral portion indicates an annular regionpresent on the periphery thereof, and the peripheral edge indicates anoutermost edge of the lens body (the back surface or the front surface).In short, the front surface and the back surface of the lens body arerespectively oriented from the optical center to the peripheral edge,and are present in the order of the center portion, the peripheralportion, and the peripheral edge.

Further, “the entire back surface is shaped in such a way as to protrudefrom the peripheral edge of the back surface, in a shape of a truncatedcone” stated herein refers to the following states.

-   -   When the lens body is viewed in a cross-section so as to pass        through the optical center, all of the portions of the back        surface from the peripheral edge toward the center portion are        disposed on the retinal side in the optical axis direction,        compared to the peripheral edge of one side (for example, upper        side of FIG. 2(f)) of the back surface,        and,    -   When the lens body is viewed in a cross-section so as to pass        through the optical center, the center portion has a shape of a        flat surface of a plateau viewed in a cross-section (shape close        to a perpendicular line in the direction of the optical axis),        compared to the peripheral portion.

By utilizing such a configuration, when the intraocular lens is insertedinto the crystal lens capsule, the center portion in the back surfaceprotrudes so as to become a plateau surface, the posterior capsule isstretched by the center portion and the center portion is stronglypressed against the posterior capsule, and thus, the intracapsularstability improves. As a result, the entry of migratory cells betweenthe posterior capsule and the lens body can be effectively suppressed,which can suppress the occurrence of a secondary cataract.

On the other hand, as shown in FIGS. 2(a) to (e), even after finallybeing subjected to all of the changes in design in the presentembodiment, it is necessary that the peripheral thickness of the lensbody (i.e., the distance between the peripheral edge of the back surfaceand the peripheral edge of the front surface) itself be remainedrelatively thin.

In this state, the peripheral portion of the back surface is shaped insuch a way as to protrude from the peripheral edge toward the centerportion as stated above. This shape is defined, for example, by theabove description regarding the back surface back surface.

At the same time, the front surface is changed in design so that theperipheral portion disposed around the center portion of the frontsurface satisfies any of the following (i) to (iii) while satisfying theprescription.

(i) The peripheral portion of the front surface is shaped in such a wayas to start to be recessed toward the retinal side in the direction ofthe optical axis when viewed toward the center from the peripheral edgeof the front surface.

(ii) The peripheral portion of the front surface is shaped in such a waythat an initial part from the peripheral edge of the front surfacetoward the center is flat.

(iii) The peripheral portion of the front surface is shaped in such away as to start to protrude from the peripheral edge of the frontsurface toward the corneal side in the direction of the optical axiswhen viewed toward the center, but, the rate of rise of the protrusionfrom the peripheral edge of the front surface is smaller than the rateof rise of the protrusion from the peripheral edge of the back surface.

Note that, FIG. 2(d) illustrates the case of (i), and FIG. 8(b) which isdescribed later illustrates the case of (iii).

Further, why the front surface of the lens body in the presentembodiment is made into the aforementioned shape is as follows.

As stated above, if the center portion of the back surface is configuredto be the plateau surface of the truncated cone, the center portion ofthe back surface certainly presses the posterior capsule strongly.

On the other hand, it is a matter of course that there is a need toachieve the prescription of the intraocular lens. Therefore, there is aneed to design the front surface to be close to a diopter which is setprior to the aforementioned Step 1, i.e., prior to the change in design.However, in addition thereto, as stated in the problem of the presentinvention, there is also a need to realize a thickness of the lens bodythat facilitates fold of the intraocular lens.

Therefore, in the present embodiment, the front surface is also changedin design in order to satisfy the prescription of the intraocular lens,while the peripheral portion disposed in the periphery of the centerportion of the front surface is changed in design in order to satisfyany of the aforementioned (i) to (iii) while satisfying theprescription.

Note that, the portion “shaped in such a way as to start to be recessed”in the aforementioned (i) is an arbitrary portion when viewed toward thecenter from the peripheral edge of the peripheral portion of the frontsurface, but for example, it may be assumed to be a portion of 1 to 2 mmfrom the peripheral edge toward the center, and of course, it may beassumed to be a wider portion (for example, the entire peripheralportion). The same may be applied to the “initial part from theperipheral edge of the front surface toward the center” of (ii), and tothe portion “shaped in such a way as to start to protrude” of (iii).

By the way, FIG. 3 is a schematic cross-sectional side view illustratingan aspect of the lens body, wherein (a) illustrates a lens body in whichthe back surface is a convex surface and a front surface is a flatsurface according to a conventional art, and meanwhile (b) illustrates astate after a change in design (corresponding to (i)) is performed tothe back surface and the front surface according to the presentembodiment.

Further, in the aforementioned (ii), “an initial part from theperipheral edge of the front surface toward the center is flat” meansthat the initial part from the peripheral edge of the front surface andthe peripheral edge toward the center are both present on the verticalplane in the direction of the optical axis. In other words, thedescription means that there are no protrusions or recesses in theinitial part from the peripheral edge of the front surface toward thecenter.

Further, in the aforementioned (iii), while the front surface ispermitted to protrude from the peripheral edge, the protrusion islimited so that “the rate of rise of the protrusion from the peripheraledge of the front surface is smaller than the rate of rise of theprotrusion from the peripheral edge of the back surface”. The meaning ofthis limitation will be described using FIG. 8 and FIG. 9.

FIG. 8 is a schematic cross-sectional side view illustrating anotherembodiment of the lens body, wherein (a) illustrates a lens body inwhich the back surface is a flat surface and the front surface is aconvex surface according to a conventional art, and (b) illustrates astate after a change in design (corresponding to (iii)) is performed tothe back surface and the front surface according to the presentembodiment.

FIG. 9 is an expanded view in the vicinity of the peripheral edge of thelens body after a change in design (iii) is performed to the lens bodyof the conventional art of FIG. 6(a) in which the back surface and thefront surface are convex surfaces. Note that, the meaning of eachundefined reference numeral will be clarified later and will be omittedat this point.

As illustrated in 8(b) and FIG. 9 (specifically, as illustrated in FIG.9), when viewed toward the center from the peripheral edge Ep of theback surface, distance Hp from a vertical plane (a surface vertical tothe direction of the optical axis (Ca-Cp). Long dash line in FIG. 9) tothe back surface passing through the peripheral edge Ep of the backsurface is set as a rate of rise of the protrusion from the peripheraledge Ep of the back surface in this specification. Similarly, distanceHa from the vertical plane to the front surface passing through theperipheral edge of the front surface Ea is set as a rate of rise of theprotrusion from the peripheral edge of the front surface Ea. In short,in the aforementioned (iii), while both the back surface and the frontsurface are protruded, Ha<Hp is satisfied at the start of theprotrusion, and the degree of the rate of rise of the protrusion of theback surface (and thus, the degree of the protrusion) is set higher thanthat of the front surface, to thereby control a thickness of theperipheral edge of the lens body.

By performing the change in design in each of the aforementioned stepsin order to satisfy any of the aforementioned (i) to (iii), it ispossible to obtain the lens body with its peripheral thickness itselfremaining relatively thin. As a result, it is possible to facilitatefold of the intraocular lens small in an injector used to inject theintraocular lens into the crystal lens capsule.

Then, if necessary, a smoothing process is performed to the centerportion and the peripheral portion of the back surface, and the centerportion and the peripheral portion of the front surface (FIG. 2(e)).This specific technique of change in design can easily be contrived by aperson skilled in the art using well-known software (for example, OpticStudio manufactured by Zemax LLC).

Note that, an example embodying the aforementioned respectivedefinitions will be Conditions 1 to 3 which are described later in <2.Intraocular lens>.

For example, a method of designing the intraocular lens according to thepresent embodiment includes the aforementioned each step. Note that, theaforementioned technique is a relatively simplified technique, and it isof course acceptable to add known contents other than the abovecontents.

The method of manufacturing the intraocular lens includes the followingsteps.

(Manufacture)

After passing through step 1 and step 2 of changing in design asdescribed above, the lens body is manufactured based final design data(FIG. 2(f)). The manufacturing technique is not specifically limited,and any known technique may be used.

2. Intraocular Lens

The lens body of the present embodiment is achieved based on a noveldesign concept described above. Therefore, the lens body in the presentembodiment also has great features as follows.

“There is provided an intraocular lens including a lens body having aback surface disposed on a retinal side and a front surface disposed ona corneal side, wherein

an entire back surface is shaped in such a way as to protrude from aperipheral edge of the back surface toward a retinal side in a directionof an optical axis, in a shape of a truncated cone toward the retinalside, and, the front surface has any of the following shapes (i) to(iii),

(i) the front surface is shaped in such a way as to start to be recessedtoward the retinal side in the direction of the optical axis when viewedtoward the center from the peripheral edge of the front surface,

(ii) the front surface is shape in such a way that an initial part fromthe peripheral edge of the front surface toward the center is flat,

(iii) the front surface is shaped in such a way as to start to protrudetoward the corneal side in the direction of the optical axis when viewedtoward the center from the peripheral edge of the front surface, but arate of rise of the protrusion from the peripheral edge of the frontsurface is smaller than a rate of rise of the protrusion from theperipheral edge of the back surface.”

The example described hereafter is a specific example which reflects adesign concept of <1. Method of designing and method of manufacturingthe intraocular lens>.

The lens body is focused upon and is described hereafter, using FIG. 4and FIG. 5. FIG. 4 is a schematic view illustrating the intraocular lensof the present embodiment, wherein (a) is a plan view, and (b) is a sidesectional view of a cross section taken along the straight broken lineviewed from the arrow X. FIG. 5 is an expanded view of a portionsurrounded by the broken line of FIG. 4.

2-1. Lens Body

The lens body is a relatively soft portion having, for example, a lensfunction, and is formed in a circular convex lens shape in a plan view.Further, as stated above, the lens body has the front surface disposedon the corneal side and the back surface disposed on the retinal side.

2-1-1. Back Surface

In the present embodiment, the shape of the back surface of the lensbody satisfies the following conditions.

-   -   In the back surface, a sag value of the back surface at a        distance Lp in a region αp within a predetermined distance from        an optical center Cp, from a virtual spherical surface Sp having        a curvature radius Rcp at the optical center Cp, with this        optical center Cp as a vertex, is not more than a sag value of        the virtual spherical surface Sp at the distance Lp.    -   On the other hand, a sag value of the back surface at a distance        lp in a region βp outside of a predetermined distance becomes        larger than the sag value of the virtual spherical surface SP at        the distance 1p.

Note that, the virtual spherical surface Sp is the virtual sphericalsurface having the optical center Cp as the vertex. The curvature radiusRcp of the spherical surface may be the curvature radius Rcp at theoptical center Cp. However, strictly speaking, as the optical center Cpitself is a point, the curvature radius cannot be measured, thus, thecurvature radius in the vicinity (For example, within a range of a 5 μmradius, or within a range of 5 □m or more) of the optical center Cp isused as the Rcp.

Further, the sag value is a vertical distance from a tangent plane atthe optical center to the virtual spherical surface Sp set as statedabove, and the distances Lp and lp are the distances from the opticalcenter when viewed parallel to the tangent plane.

Further, the region αp at a predetermined distance means a circularregion in a plan view centered at the optical center, and the region βpoutside of a predetermined distance means an annular region therearoundin a plan view.

FIG. 5 illustrates a state in which a cross-sectional shape of the backsurface in the lens body in the present embodiment satisfies theaforementioned condition.

First, the region αp (center portion) at a predetermined distance fromthe optical center Cp is focused upon in FIG. 5. Within this region αp,the sag value of the back surface of the lens body at the distance Lp isalways the same or smaller than the sag value of the virtual sphericalsurface Sp at an arbitrary distance from the optical center Cp.

This means, in short, that in the region αp at a predetermined distancefrom the optical center Cp, the back surface of an actual lens body isdisposed more on the retinal side (rearward) than the virtual sphericalsurface Sp. FIG. 5 describes a cross-section passing through the opticalcenter, but even if another cross-section passing through the opticalcenter is viewed, the lens body of the present embodiment satisfies theaforementioned conditions.

Next, the region βp outside (peripheral portion) of a predetermineddistance is focused upon in FIG. 5. In this region βp, the sag value ofthe back surface of the lens body at the distance lp is always largerthan the sag value of the virtual spherical surface Sp at an arbitrarydistance lp from the optical center Cp. This means, in short, that inthe region βp outside a predetermined distance from the optical centerCp, the back surface of the actual lens body is disposed more on thecorneal side (forward) than the virtual spherical surface Sp. In thesame manner as above, even if another cross-section passing through theoptical center is viewed, the lens body of the present embodimentsatisfies the aforementioned conditions.

Note that, it is preferable that the center portion be smoothlyconnected (as a continuous surface) with the peripheral portion in theconnection portion between the center portion and the peripheralportion.

Further, as the position of the connection portion, if r denotes theradius of the lens body, it is preferable that the portion set within arange of r*⅗ to r*⅘ is made as the connection position in terms of adistance from the optical center Cp toward the peripheral edge.

Since the shape of the back surface is configured as stated above, theposterior capsule is strongly pressed by the center portion of the backsurface, thus, the entry of the migratory cells between the posteriorcapsule and the lens body can be efficiently suppressed.

On the other hand, it is necessary to solve the problem regarding the“fold of the intraocular lens” described in the problem of the presentinvention. In order to solve this problem, the front surface of the lensbody is configured as follows.

2-1-2. Front Surface

In the present embodiment, the shape of the front surface of the lensbody satisfies the following conditions.

-   -   In the front surface, a sag value of the front surface at the        distance la in a region αa (center portion) within a        predetermined distance from the optical center Ca, from a        virtual spherical surface Sa having the curvature radius Rca at        an optical center Ca, with this optical center Ca as a vertex,        is not less than the sag value of the spherical surface Sa at        the distance La.    -   On the other hand, a sag value of the front surface at a        distance la in a region βa outside of the center portion        (peripheral portion) becomes smaller than the sag value of the        spherical surface Sa at the distance la.

The above conditions are combined with the conditions regarding the backsurface and referred to as (Condition 1).

Note that, the virtual spherical surface Sa and the sag value are thesame as those of the above description regarding the back surface. Forexample, the virtual spherical surface Sa in the front surface is avirtual spherical surface having the optical center Ca as a vertex, thesag value of the front surface is a vertical distance from the tangentplane at the optical center Ca to the virtual spherical surface Sa setas stated above, and the distances La and la are the distances from theoptical center when viewed parallel to the tangent plane.

FIG. 5 illustrates a state in which the cross-sectional shape of thefront surface in the lens body according to the present embodimentsatisfies the aforementioned conditions.

In the front surface as well, the range of the region αa (centerportion) within a predetermined distance from the optical center Ca isfocused upon in FIG. 5, in the same manner as the back surface. In thisregion αa, the sag value of the front surface of the lens body at thedistance La is always the same or larger than the sag value of thevirtual spherical surface Sa at an arbitrary distance La from theoptical center Ca.

This means that, in short, in the region αa, i.e., in the centerportion, the front surface of the actual lens body is disposed more onthe retinal side (rearward) than the virtual spherical surface Sa. WhileFIG. 5 describes a cross-section passing through the optical center, thelens body of the present embodiment satisfies the aforementionedcondition even when viewed at another cross-section passing through theoptical center.

Next, in the front surface as well, the region Pa outside of the regionwithin the predetermined distance, i.e., the peripheral portion isfocused upon in FIG. 5, in the same manner as the back surface. In thisregion Pa, the sag value of the front surface of the lens body at thedistance la is always smaller than the sag value of the virtualspherical surface Sa at an arbitrary distance la from the optical centerCa. This means that, in short, in the region βa outside of the regionwithin the predetermined distance from the optical center Ca (peripheralportion), the front surface of the actual lens body is disposed more onthe corneal side (forward) than the virtual spherical surface Sa. In thesame manner as above, the lens body of the present embodiment satisfiesthe aforementioned conditions even when viewed at another cross-sectionpassing through the optical center.

Since the above configuration is adopted, it is possible to obtain alens body with its peripheral thickness itself remaining relativelythin.

Note that, in the front surface as well, the center portion may besmoothly connected (as a continuous surface) with the peripheral portionat the connection portion between the center portion and the peripheralportion, in the same manner as the back surface. Further, as theposition of the connection portion, if r denotes the radius of the lensbody, it is preferable that the portion set within the range of r*⅗ tor*⅘ is made as the connection position in terms of the distance from theoptical center Cp toward the peripheral edge.

In this case, the connection position in the front surface may bedisposed on the portion of the front surface opposite to the directionof the optical axis (vertical direction and thickness direction) viewedfrom the connection position in the back surface, but the connectionposition may be shifted as shown in FIG. 5. To repeat, the presentembodiment, back surface shows a configuration in which the back surfaceis protruded and meanwhile the lens is made thin on the front surfacewhile realizing a predetermined prescription. Therefore, it is notnecessary that the connection position in the back surface is opposed tothe connection position in the front surface.

Note that, in addition to the aforementioned definition, the shapes ofthe back surface and the front surface after the change in design arenot specifically limited. Similarly, the shapes of the back surface andthe front surface prior to the change in design are not specificallylimited.

For example, FIG. 6 is a schematic cross-sectional side viewillustrating another aspect of the lens body, wherein (a) illustratesthe lens body in which the back surface and the front surface are convexsurfaces according to a conventional art, and (b) illustrates a stateafter a change in design (corresponding to (i)) is performed to the backsurface and the front surface according to the present embodiment.

Further, FIG. 7 is a schematic cross-sectional side view illustratinganother embodiment of the lens body, wherein (a) illustrates a lens bodyin which the back surface is a flat surface and the front surface is aconvex surface according to a conventional art, and (b) illustrates astate after a change in design (corresponding to (i)) is performed tothe back surface and the front surface according to the presentembodiment.

Further, in FIG. 8, (a) illustrates a lens body in which the backsurface is a flat surface and the front surface is a convex surfaceaccording to a conventional art, and (b) illustrates a state after achange in design (corresponding to (iii)) is performed to the backsurface and the front surface according to the present embodiment.

Therefore, the change in design shown in the present embodiment enablesthe shape satisfying the aforementioned Condition 1. This is not anexception even in the case of the aforementioned (iii), i.e., the casewhen both the front surface and the back surface protrude as illustratedin the expanded view of the vicinity of the peripheral edge of the lensbody after change in design (iii) of the lens body of the conventionalart illustrated in FIG. 6(a) in which the back surface and the frontsurface are convex surfaces.

However, as illustrated in FIG. 3, if at least a part of the frontsurface is shaped in such a way as to be recessed (preferably, theentire the front surface is recessed in a truncated cone) more than theperipheral edge of the front surface, it is possible to make the lensbody thinner, thus, this is preferable in consideration of facilitatingfold of the lens.

In addition, the diameter of the lens body may be set to any size aslong as it is a size suitable for inserting the intraocular lens intothe crystal lens capsule in an eye. A specific example of setting thesize will be described as follows. The diameter D of the lens body maybe preferably set to a range of 5 mm to 7 mm, and may be more preferablyset to 7 mm. Since a lens body with a relatively large diameter is usedwhen fixing the intraocular lens in the eye, an influence of eccentrictilting can be reduced more than a case when a lens body with a smalldiameter is used.

The thickness of the lens body may be set in accordance with a desiredrefractive index and the like. The lens body is constituted by a softmaterial which makes the lens body foldable. The term “foldable” statedherein is used with a meaning that the intraocular lens including thelens body can be folded at least in half. Therefore, the soft materialconstituting the lens body is the material having a high flexibility tothe extent that the lens body can be folded. Specifically, for example,the soft material such as silicon resin, acrylic resin, hydrogel orurethane resin may be used.

2-2. Support Portion

As long as the support portions of the present embodiment can supportthe lens body in the crystal lens capsule, the number, the shape, thematerial and the like of the support portions are not specificallylimited, and the support portions may extend arm-like from the lensbody, and may be a plate shape or a closed loop shape, but the followingmay be mentioned as an example.

The support portions of the present embodiment are formed so as toextend outward from the outer peripheral portion of the lens body. Thesupport portions are the portions that support the lens body when theintraocular lens is inserted into an eye. The two support portions areformed in one intraocular lens. Each of the support portions extend fromthe portions where an axial line passing through the center C of thelens body intersects the peripheral edge of the lens body so as to drawa circular arc in a counterclockwise direction of the respectivedrawings.

2-3. Modified Examples and Preferable Examples Relating to theIntraocular Lens

The intraocular lens of the present embodiment is not limited to theaforementioned embodiments, but includes various modifications andimprovements within the scope of deriving specific effects obtained bythe constituent features of the invention and combinations thereof

(Presence or Absence of the Support Portions)

The intraocular lens of the present embodiment includes the lens bodyand the support portions, but another member may also have a function ofsupporting the lens body in the crystal lens capsule, which is thefunction of the support portions. For example, it is also acceptablethat the lens body of the present embodiment is placed on a structurehaving a shape conforming to the crystal lens capsule, and insertedtogether into the crystal lens capsule.

However, the intraocular lens is easily folded in the presentembodiment, thus, it is preferable that the intraocular lens having thesupport portions is folded in an injector and inserted into the crystallens capsule.

Note that, if the support portions in this case are integral type withthe lens body (so-called one piece type), it is possible to sufficientlyexhibit the effect of facilitating fold of the intraocular lens.However, the present invention is not limited thereto, for example, andit is also acceptable to employ the support portions of a separate typewith the lens body.

(Sag Average Value)

The sag values of the back surface and the front surface of the lensbody of the present embodiment are respectively defined, and the sagvalues which satisfy the aforementioned definition are obtained at allpoints in the back surface and the front surface.

On the other hand, according to the examination by the present inventor,it is clear that the effect of the present invention is exhibited at allpoints in the back surface and the front surface, even if theaforementioned definition is not satisfied.

Specifically, it is clear that the effect of the present invention(i.e., the suppression of the entry of the migratory cells andfacilitating fold of the lens) is exhibited by satisfying theaforementioned definition, after replacing the “sag value” defined asdescribed above, with the “sag average value”

(Condition 2)

In the back surface, a sag average value of the back surface in theregion within a predetermined distance from an optical center Cp is notmore than a sag average value of a virtual spherical surface Sp in theregion αp within the predetermined distance from the optical center Cp,and the sag average value of the back surface in the region βp outsideof the predetermined distance from the optical center Cp becomes largerthan the sag average value of the virtual spherical surface Sp in theregion βp outside of the predetermined distance from the optical centerCp, and

in the front surface, a sag average value of the front surface in aregion in a predetermined distance from an optical center Ca is not lessthan a sag average value of a virtual spherical surface Sa in the regionαa within the predetermined distance from the optical center Ca, and thesag average value of the front surface in the region βa outside of thewithin the predetermined distance from the optical center Ca becomessmaller than the sag average value of the virtual spherical surface Sain the region βa outside of the predetermined distance from the opticalcenter Ca.

Here, the sag average value of the back surface or the virtual sphericalsurface Sp is the average value of the sag value at each point inside oroutside of the region within the predetermined distance from the opticalcenter Cp. Moreover, the sag average value of the front surface or thevirtual spherical surface Sa is the average value of the sag value ateach point inside or outside of the region within the predetermineddistance from the optical center Ca.

For example, when the sag value of the back surface or the front surfaceis measured at a predetermined number of measurement points equallyspaced from each other (for example in a grid shape), the aforementioneddefinition is not satisfied at several points, and the differencebetween the sag value of the virtual spherical surface Sp and the sagvalue of the back surface is small even if the aforementioned definitionis not satisfied, and if the aforementioned definition is satisfied atthe other points, the back surface can be sufficiently protruded. Thisis also applied to the front surface, and when the aforementionedspecification is not satisfied at several points, and the differencebetween the sag value of the virtual spherical surface Sa and the sagvalue of the front surface is small, and when the aforementioneddefinition is satisfied at the other points, the front surface has ashape which follows the definition even if the back surface protrudes,thus, it is possible to facilitate fold of the lens body or theintraocular lens, because even if the back surface is protruded, thefront surface follows the protruded shape of the back surface.

(Substantial Sag)

In addition to the sag average value, according to the examinations bythe present inventor, when the sag values of the back surface and thefront surface are measured at a predetermined number of measurementpoints equally spaced from each other, and if there are half or moremeasurement points which satisfy Condition 1 regarding theaforementioned back surface and the front surface, inside and outside ofthe region of a predetermined distance in the rear surface and the frontsurface (hereinafter, referred to as Condition 3), it is clear that theeffect of the present invention (i.e., the suppression of entry of themigratory cells and facilitating fold of the lens) is exhibited.

For example, when the sag value of the back surface or the front surfaceis measured at a predetermined number of measurement points equallyspaced from each other (for example in a grid shape), and when theaforementioned definition is not satisfied at several points, and theaforementioned definition is satisfied at the other points, the effectof the present invention is sufficiently exhibited in the same manner asstated for the sag average value mentioned earlier. Further, themeasurement points satisfying Condition 1 are preferably 80% or more ofentire the measurement points, more preferably 90% or more, and evenmore preferably 95% or more.

Note that, it is sufficient to satisfy at least one of the conditions ofthe sag value (Condition 1) given in the present embodiment, and the sagaverage value (Condition 2) given above, and the substantial sag(Condition 3). It is also acceptable to satisfy a plurality of theseconditions.

(Deviation of the Peripheral Edge from the Virtual Spherical Surface)

It is also possible to define the differences of the shapes with thevirtual spherical surface by the following expressions other than thesag value.

-   -   Peripheral edge Ep of the back surface is separated by 0.1 mm or        more from peripheral position Eps of the virtual spherical        surface Sp in a direction vertical to a tangent plane at the        optical center Cp, namely, in a direction from the back surface        to the front surface, the peripheral position Eps being located        at a distance of the peripheral edge Ep of the back surface from        the optical center Cp on the tangent plane.    -   Peripheral edge Ea of the front surface is separated by 0.1 mm        or more from peripheral position Eas of the virtual spherical        surface Sa in a direction vertical to a tangent plane at the        optical center Ca, namely, in a direction from the back surface        to the front surface, the peripheral position Eas being located        at a distance of the peripheral edge Ea of the front surface        from the optical center Ca on the tangent plane.

It is preferable to satisfy the aforementioned definition, because theshape of the lens body can be expressed more clearly, the optical partof the back surface can be sufficiently protruded with respect to theperipheral edge of the back surface and the thickness of the lens bodycan be appropriate to facilitate fold of the lens.

Note that, the peripheral edge of the back surface may be provided withan acute angle. The posterior capsule is stretched by the center portionof the back surface which makes it difficult for the migratory cells toenter, but since the peripheral edge of the back surface is providedwith the acute angle, it is possible to reduce the probability ofmigrating cells entering the gap between the back surface and theposterior capsule.

(Effective Optical Portion)

In the present embodiment, there are no limitations regarding whichportion of the lens body exhibits the optical function in accordancewith the prescription. For example, the optical function in accordancewith the prescription may be exhibited in the entire the lens body.

Conversely, the optical function may be exhibited only in apredetermined portion of the lens body. This portion is referred to asan effective optical portion. For example, the back surface and thefront surface of the lens body may respectively adopt a configurationincluding an effective optical portion which exhibits the opticalfunction in accordance with the prescription and a peripheral portiondisposed around the effective optical portion.

In this case, the peripheral portion is shaped in such a way as toprotrude, in order to dispose an effective optical portion which is acentral portion on a flat surface of the truncated cone, not only forexhibiting the optical function to realize the prescription. However, itdoes not matter if the effective optical portion has a shape forsuppressing an astigmatism which occurs in the peripheral portion.

Note that, the effective optical portion stated herein and theabovementioned central portion may or may not completely match with eachother as a region.

(Spherical and Aspherical)

The shape of the lens body of the present embodiment is not specificallylimited, and the front surface, the back surface, or both surfaces maybe spherical, aspheric, or a combination thereof.

(Monofocal and the Like)

Further, the front surface, the back surface, or both surfaces of thelens body have a shape which is at least one of monofocal, bifocal ormultifocal, or toric, the bifocal and the multifocal being refractive,diffractive, or a combination thereof. Further, a surface having a stepor a Fresnel surface may be used in a part or an entire part of theconfiguration.

3. Effect of the Embodiment

According to the present embodiment, the following effects can beobtained, in addition to the effects listed above.

To restate, first, when the intraocular lens is inserted into thecrystal lens capsule, the center portion in the back surface protrudesso as to become a plateau surface, thus, the posterior capsule isstretched by the center portion and the center portion is stronglypressed against the posterior capsule. As a result, the entry of themigratory cells between the posterior capsule and the lens body can beeffectively suppressed, and thus, the occurrence of a secondary cataractcan be suppressed.

Due to the occurrence of the aforementioned stretching to the posteriorcapsule by the center portion, wrinkles and streaks are less likely tooccur in the posterior capsule. These wrinkles and streaks may becomethe cause of optical failure (glare and the like), thus, it is useful tomake it difficult for these to occur.

Further, due to the occurrence of the aforementioned stretching, theintraocular lens is fixed in the capsule, and, it is possible tosuppress the movement, tilting, eccentricity (deviation and offset) andthe like of the intraocular lens.

Further, according to the present embodiment, the peripheral edge of thelens body can be easily wrapped in the posterior capsule. The later thetime that the intraocular lens is wrapped in the posterior capsule, thelonger the time that the gap exists between the back surface of the lensbody and the posterior capsule, and thus, the probability of entry ofthe migratory cells increases. However, in the present embodiment, theposterior capsule is stretched mainly at the center portion, thus, it isrelatively easy for the peripheral portion to contact with the posteriorcapsule. As a result, the occurrence of the secondary cataract can besuppressed.

Due to the occurrence of the aforementioned stretching, the timerequired for a contact between the back surface of the intraocular lensand the posterior capsule can be certainly reduced. As a result, theoccurrence of the secondary cataract can be suppressed.

Each of the aforementioned effects is exhibited by making the gapbetween the back surface of the intraocular lens (the lens body) and theposterior capsule as small as possible, and by making the space for thegap as small as possible. In other words, the contact area between theback surface of the lens body and the posterior capsule is made as largeas possible.

Further, the intraocular lens of the present embodiment is particularlyeffective for a toric lens, because it is predicted that rotation of thepostoperative intraocular lens (IOL) can be decreased, and intracapsularstability can be improved.

Further, facilitating fold of the intraocular lens is provided as asubject of the present invention, but according to the presentembodiment, the back surface protrudes in a shape of a truncated cone,while the front surface is changed in design so as to be in the case ofany of (i) to (iii) (i.e., the rate of rise of the protrusion of thefront surface is smaller or recessed than the rate of rise of theprotrusion of the back surface). Therefore, the lens body can be maderelatively thin, and it is possible to fold the intraocular lensrelatively easily. Specifically, when the intraocular lens of thepresent embodiment is one piece type, it is possible to facilitate afolding operation even in a case that the support portion is folded andwrapped in the lens body.

As described above, according to the present embodiment, the intraocularlens is provided, which improves intracapsular stability and suppressesthe occurrence of the secondary cataract while facilitating fold of theintraocular lens.

4. Modification Examples

The technical scope of the present invention is not limited to theaforementioned embodiments, but includes various modifications andimprovements within the scope of deriving specific effects obtained bythe constituent features of the invention and combinations thereof

(Applications Other than Insertion into the Crystal Lens Capsule)

The intraocular lens of the present embodiment is based on the insertioninto the crystal lens capsule (in the bag), but is not limited to thisapplication. For example, the intraocular lens of the present embodimentis also useful in the case of an out the bag application in which theintraocular lens is disposed outside of the crystal lens capsule andbetween the iris and the crystal lens capsule. The reason therefore isthat the back surface of the lens body in the intraocular lens of thepresent embodiment is shaped in such a way as to protrude to the retinalside, and the front surface is disposed relatively close to the retina.With this shape, it is possible to reduce the chance of contact with theiris present on the corneal side of the intraocular lens.

(Definition 1 of Shape of the Lens Body)

In addition to the definition using the sag value as stated above, it isalso possible to define the shapes of the back surface and the frontsurface, particularly the protrusion shape of the back surface asfollows.

“An intraocular lens including a lens body having two opposing surfacesA and B, wherein

the entire surface A has a shape protruding in a shape of a truncatedcone from a peripheral edge of the surface A and the entire surface Bhas a shape which is recessed from a peripheral edge of surface B towardone of the optical axis directions.”

In the aforementioned definition, in consideration of the applicationsother than insertion into the crystal lens capsule, the positionalrelationship between the front surface, the back surface, the anteriorcapsule, and the posterior capsule is not defined.

In the surface A which corresponds to the back surface of the lens bodyof the present embodiment, the entire back surface protrudes withrespect to the peripheral edge. However, the shape at this time is atruncated cone-shape. In short, the central portion corresponds to theplateau surface of the truncated cone, and the peripheral portioncorresponds to a portion of the truncated cone. The connection portiondescribed above is present at the boundary between the central portionand the peripheral portion. The connection portion and the positionthereof are as stated in the present embodiment.

Further, in the surface B which corresponds to the front surface of thelens body of the present embodiment, contrary to the surface A, theentire surface B has a recessed shape with respect to the peripheraledge of the surface B. Here, the term “recessed” indicates that thesurface B is disposed at a position recessed from the plane formed bythe peripheral edge of the surface B. However, the vertex of the surfaceB may be present on the plane.

Note that, with regards to the surface B, the definition regarding thefront surface in the above described Condition 1 may be adopted.

(Definition 2 of the Shape of the Lens Body)

The following is given as another definition.

“An intraocular lens including a lens body having a front surfacedisposed on a corneal side and a back surface disposed on a retinalside, wherein, the lens body, viewed from a peripheral edge of the lensbody, has a shape which is bent toward the retinal side in a directionof an optical axis.”

The aforementioned definition is different than specification 1, anddefines an arrangement relationship between the back surface and thefront surface when the intraocular lens is inserted into the eye. On theother hand, the expression “bent” is used as the shape of the backsurface. This shows a state in which a region closer to the center thanthe peripheral edge of the back surface is disposed on the retinal side(rearward) compared to the peripheral edge of the back surface (inshort, a state in which the peripheral edge is disposed closest to thecorneal side in the back surface, for example, as illustrated in FIG.3(b), FIG. 6(b) and FIG. 7(b)). On the other hand, the front surface maybe in a state in which the region closer to the center than theperipheral edge of the front surface is disposed on the retinal side(rearward) compared to the peripheral edge of the front surface (inshort, a state in which the peripheral edge is disposed closest to thecorneal side in the back surface, for example, as illustrated in FIG.3(b) and FIG. 6(b)), or, in a state in which the above region exists onthe same plane as a plane formed by the peripheral edge of the frontsurface. Of course, it is preferable that an entire front surface isdisposed on the retinal side (rearward) compared to the peripheral edgeof the front surface. This is because the lens body can be made thin,and fold of the lens can be further facilitated.

Note that, regarding the front surface, the definition regarding thefront surface in the above described Condition 1 may be adopted.

(Definition 3 of the Shape of the Lens Body)

The aforementioned definition: “satisfies at least one of Conditions 1to 3” is given as a specific example, but it is also possible to regardthis definition itself as an invention which is not dependent upon thecases (i) to (iii). Even in this case, the effect of the presentinvention is exhibited as described in detail in the present embodiment.

LIST OF REFERENCE SIGNS

-   1 . . . Intraocular lens-   2 . . . Lens body-   3 . . . Support portion-   100 . . . Intraocular lens-   200 . . . Lens body-   300 . . . Support portion-   Cp . . . Optical center of back surface-   Sp . . . Virtual spherical surface of back surface-   Rcp . . . Curvature radius of virtual spherical surface Sp-   Ep . . . Peripheral position of back surface-   Eps . . . Peripheral position of virtual spherical surface Sp-   αp . . . Center portion of back surface-   βp . . . Peripheral portion of back surface-   Ca . . . Optical center of front surface-   Sa . . . Virtual spherical surface of front surface-   Rca . . . Curvature radius of virtual spherical surface Sa-   Ea . . . Peripheral position of front surface-   Eas . . . Peripheral position of virtual spherical surface Sa-   αa . . . Center portion of front surface-   βa . . . Peripheral portion of front surface

The invention claimed is:
 1. An intraocular lens, comprising: a lensbody having a back surface with a peripheral edge and an optical centerCp and a front surface with a peripheral edge and an optical center Ca,wherein the back surface is shaped in such a way as to extend from theback surface peripheral edge toward the back surface optical center in adirection of an optical axis, a peripheral portion cross-section has atruncated cone shape, and the front surface has any of the followingshapes (i) to (iii): (i) the front surface is shaped in such a way as tostart to be recessed toward the retinal side in the direction of theoptical axis when viewed toward the optical center from the frontsurface peripheral edge, (ii) the front surface is shaped in such a waythat an initial part from the front surface peripheral edge toward thecenter is flat, (iii) the front surface is shaped in such a way as tostart to extend toward a corneal side in the direction of the opticalaxis when viewed toward the center from the front surface peripheraledge, but a rate of rise of a protrusion from the front surfaceperipheral edge is smaller than a rate of rise of a protrusion from theback surface peripheral edge, and wherein at least one of the followingconditions is satisfied: Condition 1 in the back surface, a sag value ofthe back surface at a distance Lp in a region within a predetermineddistance from the optical center Cp, to a virtual spherical surface Sphaving a curvature radius Rcp at the optical center Cp, with thisoptical center Cp as a vertex, is not more than a sag value of thevirtual spherical surface Sp at the distance Lp, and a sag value of theback surface at a distance lp outside of the region within thepredetermined distance becomes larger than a sag value of the virtualspherical surface Sp at the distance lp, and in the front surface, a sagvalue of the front surface at a distance La in a region within apredetermined distance from the optical center Ca, to a virtualspherical surface Sa having a curvature radius Rca at the optical centerCa, with this optical center Ca as a vertex, is not less than a sagvalue of the virtual spherical surface Sa at the distance La, and a sagvalue of the front surface at a distance la outside of the region withinthe predetermined distance becomes smaller than a sag value of thevirtual spherical surface Sa at the distance la, Condition 2 in the backsurface, a sag average value of the back surface in a region within apredetermined distance from the optical center Cp is not more than a sagaverage value of the virtual spherical surface Sp in the region withinthe predetermined distance, and a sag average value of the back surfaceoutside of the region within the predetermined distance becomes largerthan a sag average value of the virtual spherical surface Sp outside ofthe region within the predetermined distance, and in the front surface,a sag average value of the front surface in a region within apredetermined distance from the optical center Ca is not less than a sagaverage value of the virtual spherical surface Sa inside of the regionwithin the predetermined distance, and a sag average value of the frontsurface outside of the region within the predetermined distance becomessmaller than a sag average value of the virtual spherical surface Saoutside of the region within the predetermined distance, Condition 3 inthe back surface and the front surface, when the sag values thereof aremeasured at a predetermined number of measurement points equally spacedfrom each other, there are half or more measurement points which satisfyCondition 1, inside and outside of the region within the predetermineddistance, wherein the sag value is a vertical distance from a tangentplane at the optical center, to the virtual spherical surface, distancesLp, lp, La and la are the distances from the optical center when viewedin parallel to the tangent plane, the sag average value of the backsurface or the virtual spherical surface Sp is the average value of thesag value at each point inside or outside of the region within thepredetermined distance from the optical center Cp, and the sag averagevalue of the front surface or the virtual spherical surface Sa is theaverage value of the sag value at each point inside or outside of theregion within the predetermined distance from the optical center Ca. 2.The intraocular lens according to claim 1, wherein a peripheral positionEp of the back surface is separated by 0.1 mm or more from a peripheralposition Eps of the virtual spherical surface Sp in a direction verticalto a tangent plane at the optical center Cp, namely, in a direction fromthe back surface to the front surface, the peripheral position Eps beinglocated at a distance of a peripheral edge Ep of the back surface fromthe optical center Cp on the tangent plane, and a peripheral position Eaof the front surface is separated by 0.1 mm or more from a peripheralposition Eas of the virtual spherical surface Sa in a direction verticalto a tangent plane at the optical center Ca, namely, in a direction fromthe back surface to the front surface, the peripheral position Eas beinglocated at a distance of a peripheral edge Ea of the front surface fromthe optical center Ca on the tangent plane.
 3. The intraocular lensaccording to claim 1, wherein an optical function in accordance with aprescription is exhibited in an entire lens body.
 4. The intraocularlens according to claim 1, wherein the back surface and the frontsurface of the lens body respectively include an effective opticalportion which exhibits an optical function in accordance with aprescription and the peripheral portion disposed around the effectiveoptical portion.
 5. The intraocular lens according to claim 1, whereinthe front surface, the back surface, or both surfaces of the lens bodyis spherical, aspheric, or a combination thereof.
 6. The intraocularlens according to claim 1, wherein at least one of the front surface orthe rear surface has a shape selected from the group consisting ofmonofocal, bifocal, multifocal and toric, the bifocal shape is at leastone of refractive or diffractive, and the multifocal shape is at leastone of refractive or diffractive.
 7. The intraocular lens according toclaim 1, further comprising: a support portion extending from the lensbody.